Can the same hostname be used in different namespaces in Kubernetes?

Описание: Explore how to use the same `hostname` across different `namespaces` in Kubernetes without conflicts using unique paths or subdomains.
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This video is based on the question https://stackoverflow.com/q/64012806/ asked by the user 'devcloud' ( https://stackoverflow.com/u/12371863/ ) and on the answer https://stackoverflow.com/a/64013732/ provided by the user 'Luis Gonzalez' ( https://stackoverflow.com/u/6673573/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Can the Same Hostname Be Used in Different Namespaces in Kubernetes?

In the world of Kubernetes, managing hostnames and namespaces can sometimes feel overwhelming, especially when you want to utilize the same hostname for multiple services. This leads to the question: Can the same hostname be used in different namespaces in Kubernetes without causing conflicts? If you’ve tried to set this up and run into trouble, you’re not alone. Let's dive into the solution to this common issue.

The Challenge

You are set on using the hostname example.com in two different namespaces. The first namespace is dedicated to production (prod), while the second is for development (dev). The desired URLs are:

example.com/prod/static

example.com/dev/static

example.com/demo

However, when testing this configuration, you find that your NGINX ingress controller defaults to the first one, leading to confusion and accessibility issues for not only developers but also stakeholders relying on these deployments.

The Solution: Managing Hostnames Across Namespaces

You can successfully use the same hostname in different namespaces in Kubernetes by defining unique paths for your applications. Here are the steps you should take to make this work effectively:

1. Define Unique Paths for Each Namespace

Instead of letting both namespaces listen on the same base path, you can specify distinct paths to route the traffic correctly:

Production Namespace Configuration

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Development Namespace Configuration

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2. Resulting Traffic Management

With these configurations, your traffic routing will function as follows:

example.com/prod/static ➔ points to app-svc:80 on prod-env namespace

example.com/prod/ ➔ points to app-svc:8000 on prod-env namespace

example.com/dev/static ➔ points to app-svc:80 on dev-env namespace

example.com/demo ➔ points to app-svc:8000 on dev-env namespace

3. Consider Using Subdomains for Cleaner Routing

If you prefer to preserve the URL structure after the host, configuring subdomains may be a more user-friendly approach. This would require adjusting your DNS settings to include A records for each subdomain:

Subdomain Configurations

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DNS Setup for Subdomains

To implement subdomains, add A records in your DNS management panel. Here’s an example of what that might look like:

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Alternatively, you can use a wildcard subdomain entry to simplify the process:

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Conclusion

Using the same hostname in different namespaces in Kubernetes is entirely feasible when configured correctly. By defining unique paths or utilizing subdomains, you can effectively manage your applications without conflict. This setup not only organizes access points for different environments but also ensures clarity for all team members and stakeholders by providing distinct routes for services without ambiguity.

For those venturing into advanced Kubernetes networking, remember that keeping your Ingress resources orderly is crucial for efficient operations.